Method of producing composite articles



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Patented June 7, 1932 UNITED STATES EENRY'L. WARD, OF CHICAGO, ILLINOIS, ASBIGNOB TO INCORPORATED, OF NEW YORK, N. Y.,IA' OORPUB'ATIONUFQNFEW.YOBK

METHOD OF YRODUGING"UOMPO8ITE5AB!IM No Drawing.

This invention relates to a method of producing composite articles comprising fibrous material and rubber.

Materials which are employed as separators for spring contacts for electrical switches and the like, or in panels for mounting electrical apparatus, besides being insulators,' must possess requisite characteristics of tensile strength, hardness and rigidity. -Socalled phenol fibre satisfiesmost of these requirements but it is expensive in price. Hardrubber possesses many of the same requisite qualities and is comparatively chea in rice; but it is subject to cold flow an this in time may cause war ing and stretching of the article formed t erefrom which may require frequent adjustment of the spring contacts or other apparatus supported thereby.

The object of this invention is to reduce a material which will be stron ,har and not subject to objectionable cold ow; and which at the same time will be cheap in price.

In accordance with the main feature of the invention rubber and. suflicient sul hur to cause com lete vulcanizationof theru her are introduce into fibroussheets by impregnatin said fibrous sheets with an emulsion or a so ution of rubber and sulphur in a suitable liquid. After impregnation the sheets are dried, then stacked in sufiicient quantity to produce the thickness desired, and finally subjected to heat and pressure to thoroughly vulcanize the rubber, and form the fibrous sheets and ingrained rubber into a firm composite structure.

Although various types of fibrous sheets may be employed, it is preferable to use aporous paper which is highly absorbent, strong and entirely free from electricity conducting materials. A pure cotton-linter paper has been found to possess these characteristics.

The rubber ma be introduced into the paper by means 0 an emulsion of rubber in water, by means of the natural latex, by means of a solution of rubber in an organic solvent, or by mechanical means. It is preferable, however, to emplo rubber in the emulsified form or latex arm, which is a natural water emulsion. The sulphur ma be introduced in a number of ways. Goo remaimed; suip'hur.

. suflicient; quantity.

treated with Application fled s ut 9. 1m seriailnaiuimi.

suits may he grinding *the sulcent by weightmf therubber in the latex. A greater jijj'iceutage ofvsulphun namely as much as -E'l'fhrzaay.be;satisfactoiri1yused without deleteriougg ailectingithequality of'the article rad i :Gacailresultsmaybe obcwevegmy employing'itboutvulcanization .msemr er standard such as;diphenylguanidinemay alsobe .added withfithe sulphur. 'The amountof sulphur maybeldecreased if a largeanmount of 'acceleratoris used, or .may be entirely done away employi :so called :ultrwacceleratorg'suchms zinc-e yl+xenthozenate in lei'lgdf rqper guilitiesfhauingheen rlihber initheamunner described, it is thoroughly firied by exposure to the air or'by artificial means, such as by subj'ecting it to an ovenitreatment-ortoablastofdry,

heated air. f This latter may cause partial vulcanization of the rubber, which may even be desirable'if not continued'too far, because the time of treatment of the stacked sheets under pressure can then be reduced.

The treated and dried sheets are then arranged to produce the desired product, and fina 1y 'Slilflflflifid to -:liea'itaml high pressure to completely vulcanize 'the rubber. Theheat and ressure cause a further impregnationof "the bres of'the paper and'have-the effect of joining the individual sheets into a composite structure, having the characteristics of hard rubber with added strength rigidity and resistance to cold flow.

The composite material is equivalent to hard rubber for insulation purposes and machines easily, being at the same time as cheap in price as hard rubber and cheaper in price than materials it can "be used to supplant.

This'material maybe employed to separate the s ring contacts of switches such as key switciies which are used on telephone switchboards. In this type of switch, spring coni I Leagues tacts are separated by suitable electrical insulating material; which must possess enough strength and hardness to prevent the spring contacts from losing their ad'ustment by he- 75 coming loose. This improv material being hard and resistant to cold flow can be efiectively used in this manner.- Besides the use described in the precedin aragralph it is obvious that the materia erein, escribed may beused for telephone switchboard; and other panels for mounting electrical apparatus, and in other laces where such qualities as-'cheapness,' ha ess, rigidity and resistance to cold flow are desired in an electrical insulating material.

What is claimed is:

1; The method of producing a composite insulator whichconsists in" impregnating highly'absorbent paper sheets free from electrlcity conducting materials with rubber and a vulcanizing agent, heating the im regnated sheets to vulcamze partially the rub r therein, assembling a plurality of im regnated sheets, and su jectmg the assemble sheets to 95 heat and pressure until the rubber therein is completely vulcanized. p

2. A method of'producing a composite insulator which consists in impregnating highly absorbent paper sheets free from elec- Ptncity conduct' materials with a rubber solution and a canizing agent, heating the im regnated sheets to vulcanize partiall the ru ber therein, assemblin a plurality o imgrzfnated sheets; and en jecting the assem- 1 sheets to heat and pressure until the rubber therein is completely vulcanized.

In witness whereof, I hereunto subscribe my name this 29th dafiif July A. Dr 1924.

NR L. WARD. 

